I have a 2007 cobalt lt with pioneer audio and xm but no on-star. I replaced by HU a few years ago and want to get Sirius again(now have a kdc bt555u). Does anyone have a thread or know how to do this. From what I gather, I would have to take the back deck out and unhook the antenna cable from the Sirius box, then get an extender and wire it to my Sirius ready HU by using a Sirius sxv200 adapter. Please Help.